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1. (Article ID: 5789)
 
Kenyon JJ, Senchenkova SN, Shashkov AS, Shneider MM, Popova AV, Knirel YA, Hall RM
K17 capsular polysaccharide produced by Acinetobacter baumannii isolate G7 contains an amide of 2-acetamido-2-deoxy-D-galacturonic acid with D-alanine
International Journal of Biological Macromolecules 144 (2020) 857-862
 

The K17 capsular polysaccharide (CPS) produced by Acinetobacter baumannii G7, which carries the KL17 configuration at the capsule biosynthesis locus, was isolated and studied by chemical methods along with one- and two-dimensional 1H and 13C NMR spectroscopy. Selective cleavage of the glycosidic linkage of a 2,4-diacetamido-2,4,6-trideoxy-D-glucose (D-QuiNAc4NAc) residue by (i) trifluoroacetic acid solvolysis or (ii) alkaline β-elimination (NaOH-NaBH4) of the 4-linked D-alanine amide of a 2-acetamido-2-deoxy-D-galacturonic acid residue (d-GalNAcA6DAla) yielded trisaccharides that were isolated by Fractogel TSK HW-40 gel-permeation chromatography and identified by using NMR spectroscopy and high-resolution electrospray ionization mass spectrometry. The following structure was established for the trisaccharide repeat (K unit) of the CPS: →4)-α-D-GalpNAcA6DAla-(1→4)-α-D-GalpNAcA-(1→3)-β-D-QuipNAc4NAc-(1→. The presence of the itrA1 gene coding for the initial glycosylphosphotransferase in the KL17 gene cluster established the first sugar of the K unit as D-QuipNAc4NAc. KL17 includes genes for three transferases that had been annotated previously as glycosyltransferases (Gtrs). As only two Gtrs are required for the K17 structure and one D-GalpNAcA residue is modified by a D-alanine amide, these assignments were re-assessed. One transferase was found to belong to the ATPgrasp_TupA protein family that includes D-alanine-D-alanine ligases, and thus was renamed Alt1 (alanine transferase). Alt1 represents a novel family that amidate the carboxyl group of D-GalpNAcA or D-GalpA.

Acinetobacter baumannii, capsular polysaccharide, D-alanine, K locus, KL17

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2. (Article ID: 5791)
 
Knirel YA, Van Calsteren M
Bacterial exopolysaccharides
Book: Comprehensive Glycoscience: From Chemistry to Systems Biology. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering (2021) 1-75
 

Bacterial extracellular polysaccharides are known as a cell-bound capsule, a sheath, or a slime, which is excreted into the environment. They play an important role in virulence of medical bacteria and plant-to-symbiont interaction and are used for serotyping of bacteria and production of vaccines. Some exopolysaccharides have commercial applications in industry, and claims of health benefits have been documented for an increasing number of them. Exopolysaccharides have diverse composition and structure, and some contain sugar and non-sugar components that are found in bacterial carbohydrates only. The present article provides an updated collection of the data on exopolysaccharides of various classes of gram-negative and gram-positive bacteria reported until the end of 2019. When known, biosynthesis pathways of exopolysaccharides are treated in a summary manner. References are made to structure and biosynthesis relatedness between exopolysaccharides of different bacterial taxa as well as between bacterial polysaccharides and mammalian glycosaminoglycans.

polysaccharide structure, Gram-negative bacteria, capsule, Biofilm, polysaccharide biosynthesis, gram-positive bacteria, Monosaccharide composition, Bacterial exopolysaccharide, non-sugar component

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3. (Article ID: 6411)
 
Kasimova AA, Sharar NS, Ambrose SJ, Knirel YA, Shneider MM, Timoshina OY, Popova AV, Perepelov AV, Dmitrenok AS, Hsu LY, Hall RM, Kenyon JJ
The Acinetobacter baumannii K70 and K9 capsular polysaccharides consist of related K-units linked by the same Wzy polymerase and cleaved by the same phage depolymerases
Microbiology Spectrum 11(6) (2023) e0302523
 

Bacteriophage show promise for the treatment of Acinetobacter baumannii infections that resist all therapeutically suitable antibiotics. Many tail-spike depolymerases encoded by phage that are able to degrade A. baumannii capsular polysaccharide (CPS) exhibit specificity for the linkage present between K-units that make up CPS polymers. This linkage is formed by a specific Wzy polymerase, and the ability to predict this linkage using sequence-based methods that identify the Wzy at the K locus could assist with the selection of phage for therapy. However, little is known about the specificity of Wzy polymerase enzymes. Here, we describe a Wzy polymerase that can accommodate two different but similar sugars as one of the residues it links and phage depolymerases that can cleave both types of bond that Wzy forms.

Acinetobacter baumannii, capsular polysaccharide, Wzy polymerase, phage depolymerase, K70

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